U.S. patent application number 10/594400 was filed with the patent office on 2007-07-19 for method and apparatus for controlling at least one ventilation parameter of an artificial ventilator for ventilating the lung of a patient in accordance with a plurality of lung positions.
This patent application is currently assigned to KCI LICENSING, INC.. Invention is credited to Stephan Bohm, Royce W. Johnson.
Application Number | 20070163584 10/594400 |
Document ID | / |
Family ID | 35064329 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070163584 |
Kind Code |
A1 |
Bohm; Stephan ; et
al. |
July 19, 2007 |
Method and apparatus for controlling at least one ventilation
parameter of an artificial ventilator for ventilating the lung of a
patient in accordance with a plurality of lung positions
Abstract
The invention refers to a method and an apparatus for
controlling at least one ventilation pressure of an artificial
ventilator for ventilating an artificially ventilated lung of a
patient in accordance with a plurality of lung positions. In order
to improve the potentials of the kinetic rotation therapy, at least
one ventilation pressure is controlled in accordance with a defined
lung position and in accordance with a lung status information
related to said defined lung position.
Inventors: |
Bohm; Stephan; (Hamburg,
DE) ; Johnson; Royce W.; (Universal City,
TX) |
Correspondence
Address: |
LEGAL DEPARTMENT INTELLECTUAL PROPERTY;KINETIC CONCEPTS, INC.
P.O. BOX 659508
SAN ANTONIO
TX
78265-9508
US
|
Assignee: |
KCI LICENSING, INC.
8023 Vantage Drive
San Antonio
TX
78230-4726
|
Family ID: |
35064329 |
Appl. No.: |
10/594400 |
Filed: |
March 29, 2005 |
PCT Filed: |
March 29, 2005 |
PCT NO: |
PCT/US05/10741 |
371 Date: |
September 26, 2006 |
Current U.S.
Class: |
128/204.18 ;
128/200.24; 128/204.21 |
Current CPC
Class: |
A61M 2230/65 20130101;
A61M 2230/432 20130101; A61M 2230/205 20130101; A61M 2230/432
20130101; A61M 2230/205 20130101; A61M 2230/005 20130101; A61M
2230/005 20130101; A61G 7/008 20130101; A61M 2016/0036 20130101;
A61M 2230/65 20130101; A61M 2230/005 20130101; A61M 16/022
20170801; A61M 2205/52 20130101 |
Class at
Publication: |
128/204.18 ;
128/200.24; 128/204.21 |
International
Class: |
A61M 16/00 20060101
A61M016/00; A62B 7/00 20060101 A62B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2004 |
EP |
04 007 580.6 |
Mar 11, 2005 |
EP |
05 005 418.8 |
Claims
1. A recording method to record a status of an artificially
ventilated lung of a patient in accordance with a plurality of lung
positions, the patient lying in a nursing bed and a position of the
artificially ventilated lung is moveable by a position actuator,
comprising the steps of: a) moving the artificially ventilated lung
by the position actuator to a defined lung position, b) determining
the status of the artificially ventilated lung, and c) recording
the status of the artificially ventilated lung in accordance with
the defined lung position.
2. The recording method of claim 1, wherein the nursing bed is
rotatable around its longitudinal axis and wherein the position
actuator is a motor rotating the nursing bed around its
longitudinal axis.
3. The recording method of claim 1, wherein the position actuator
comprises air cushions provided underneath the patient.
4. The recording method of claim 1, wherein the defined lung
position is reached by a predetermined step size of the position
actuator.
5. The recording method of claim 1, wherein the defined lung
position is reached in accordance with a feed back signal of a
position sensor measuring the actual lung position.
6. The recording method of claim 1, wherein the status of the
artificially ventilated lung includes a measure of a regional or a
global information on lung morphology and/or lung function.
7. The recording method of claim 1, wherein the status of the
artificially ventilated lung includes a measure of the
functionality with regard to the global gas exchange of the
lung.
8. The recording method of claim 1, wherein the determined status
of the artificially ventilated lung includes recording by a
computer in accordance with the corresponding defined lung
position.
9. The recording method of claim 1, wherein the steps a), b), and
c) are repeated with a predetermined differential step size of the
position actuator until the status of the artificially ventilated
lung has been determined over a predetermined range of lung
positions.
10. A controlling method to control at least one ventilation
pressure of an artificial ventilator for ventilating an
artificially ventilated lung of a patient in accordance with a
plurality of lung positions, the patient lying in a nursing bed and
the position of the artificially ventilated lung is moveable by a
position actuator, comprising the steps of: a) obtaining lung
status information which is based on at least two supporting points
of a first status of the artificially ventilated lung in accordance
with a first lung position and a second status of the artificially
ventilated lung in accordance with a second lung position, b)
moving the artificially ventilated lung by the position actuator to
a defined lung position, c) controlling of at least one ventilation
pressure in accordance with the defined lung position and in
accordance with the lung status information related to said defined
lung position.
11. (canceled)
12. The controlling method of claim 10, wherein the lung status
information is interpolated between the supporting points in
accordance with the difference between two neighboring supporting
points.
13. The controlling method of claim 10, wherein at least one
ventilation pressure is controlled such that the lung status
information yields a homogeneous distribution over a plurality of
lung positions.
14. A positioning method to control the change of a position of an
artificially ventilated lung of a patient, the patient lying in a
nursing bed and the position of the artificially ventilated lung is
changeable by a corresponding position actuator, comprising the
steps of: a) providing a periodical controlling signal having a
distribution of a plurality of position periods and/or of a
plurality of amplitudes, b) controlling the position actuator by
said periodical controlling signal.
15. The positioning method of claim 14, wherein the distribution is
compiled via a user's interface on the basis of a given set of
periodical controlling signals.
16. The positioning method of claim 14, wherein the distribution is
compiled in accordance with lung status information which is based
on at least two supporting points of a first status of the
artificially ventilated lung in accordance with a first lung
position and a second status of the artificially ventilated lung in
accordance with a second lung position.
17. A recording apparatus to record a status of an artificially
ventilated lung of a patient lying in a nursing bed in accordance
with a plurality of lung positions, comprising: a) a position
actuator to move the artificially ventilated lung to a defined lung
position, b) determining means to determine the status of the
artificially ventilated lung, and c) recording means to record the
status of the artificially ventilated lung in accordance with the
defined lung position.
18. The recording apparatus of claim 17, wherein the nursing bed is
rotatable around its longitudinal axis and wherein the position
actuator is a motor rotating the nursing bed around its
longitudinal axis.
19. The recording apparatus of claim 17, wherein the position
actuator comprises air cushions provided underneath the
patient.
20. The recording apparatus of claim 17, wherein the defined lung
position is reached by a predetermined step size of the position
actuator.
21. The recording apparatus of claim 17, wherein the defined lung
position is reached in accordance with a feed back signal of a
position sensor measuring the actual lung position.
22. The recording apparatus of claim 17, wherein the status of the
artificially ventilated lung is a measure of a regional or a global
information on lung morphology and/or lung function.
23. The recording apparatus of claim 17, wherein the status of the
artificially ventilated lung is a measure of the functionality with
regard to the global gas exchange of the lung.
24. The recording apparatus of claim 17, wherein the determined
status of the artificially ventilated lung is recorded by a
computer in accordance with the corresponding defined lung
position.
25. The recording apparatus of claim 17, wherein a predetermined
differential step size is applied repeatingly to the position
actuator until the status of the artificially ventilated lung has
been determined over a predetermined range of lung positions.
26. A controlling apparatus to control at least one ventilation
pressure of an artificial ventilator for ventilating an
artificially ventilated lung of a patient lying in a nursing bed in
accordance with a plurality of lung positions, comprising: a) means
for obtaining lung status information which is based on at least
two supporting points of a first status of the artificially
ventilated lung in accordance with a first lung position and a
second status of the artificially ventilated lung in accordance
with a second lung position, b) a position actuator to move the
artificially ventilated lung to a defined lung position, c) means
for controlling of at least one ventilation pressure in accordance
with the defined lung position and in accordance with the lung
status information related to said defined lung position.
27. The controlling apparatus of claim 26, wherein the lung status
information is obtained by using the recording apparatus according
to claim 25.
28. The controlling apparatus of claim 26, wherein the lung status
information is interpolated between the supporting points in
accordance with the difference between two neighbouring supporting
points.
29. The controlling apparatus of claim 26, wherein at least one
ventilation pressure is controlled such that the lung status
information yields a homogeneous distribution over a plurality of
lung positions.
30. A positioning apparatus to control the a change of a position
of an artificially ventilated lung of a patient lying in a nursing
bed, comprising: a) a position actuator for changing the position
of the artificially ventilated lung, b) means for providing a
periodical controlling signal having a distribution of a plurality
of position periods and/or of a plurality of amplitudes, and c)
means for controlling the position actuator by said periodical
controlling signal.
31. The positioning apparatus of claim 30, wherein the distribution
is compiled via a user's interface on the basis of a given set of
periodical controlling signals.
32. The positioning apparatus of claim 30, wherein the distribution
is compiled in accordance with lung status information which is
based on at least two supporting points of a first status of the
artificially ventilated lung in accordance with a first lung
position and a second status of the artificially ventilated lung in
accordance with a second lung position.
33. The controlling method of claim 10, wherein the lung status
information is obtained by a recording method, the recording method
to record a status of an artificially ventilated lung of a patient
in accordance with the plurality of lung positions, the recording
method comprising the steps of: a) moving the artificially
ventilated lung by the position actuator to a defined lung
position, b) determining the status of the artificially ventilated
lung, c) recording the status of the artificially ventilated lung
in accordance with the defined lung position, and repeating the
steps a), b), and c) with a predetermined differential step size of
the position actuator until the status of the artificially
ventilated lung has been determined over a predetermined range of
lung positions.
Description
[0001] The invention refers to a method and apparatus for recording
the status of an artificially ventilated lung of a patient in
accordance with a plurality of lung positions and to a method and
apparatus for controlling at least one ventilation parameter of an
artificial ventilator for ventilating an artificially ventilated
lung of a patient in accordance with a plurality of lung positions.
Furthermore, the invention refers to a method and an apparatus for
controlling the change of the position of an artificially
ventilated lung of a patient. For carrying out the invention it is
assumed that the patient lies in a nursing bed and that the
position of the artificially ventilated lung is movable or
changeable by a position actuator. An example for such a nursing
bed is a rotation bed which is rotatable by a rotation angle around
its longitudinal axis.
[0002] The treatment of acute lung failure, acute lung injury (ALI)
and acute respiratory distress syndrome (ARDS) is still one of the
key problems in the treatment of severely ill patients in the
intensive care unit. Despite intensive research over the past two
decades the negative implications of respiratory insufficiency are
still affecting both the short and long term outcome of the
patient. While different ventilator strategies have been designed
to treat the oxygenation disorder and to protect the lungs from
ventilator induced lung injury, additional therapeutic options were
evaluated.
[0003] Dynamic body positioning (kinetic or axial rotation therapy)
was first described by Bryan in 1974. This technique is known to
open atelectasis and to improve lung function, particularly
arterial oxygenation in patients with ALI and ARDS. Since kinetic
rotation therapy is a non-invasive and relatively inexpensive
method it can even be used prophylactically in patients whose
overall health condition or severity of injury predispose to lung
injury and ARDS. It could be shown that the rate of pneumonia and
pulmonary complications can be reduced while survival increased if
kinetic rotation therapy is started early on in the course of a
ventilator treatment. This therapeutic approach may reduce the
invasiveness of mechanical ventilation (i.e. airway pressures and
tidal volumes), the time on mechanical ventilation and the length
of stay on an intensive care unit.
[0004] Kinetic rotation therapy in the sense of the present
invention is applied by use of specialized rotation beds which can
be used in a continuous or a discontinuous mode with rests at any
desired angle for a predetermined period of time. The general
effect of axial rotation in respiratory insufficiency is the
redistribution and mobilization of both intra-bronchial fluid
(mucus) and interstitial fluid from the lower (dependent) to the
upper (non-dependent) lung areas which will finally lead to an
improved matching of local ventilation and perfusion. As a
consequence, oxygenation increases while intra-pulmonary shunt
decreases. Lymph flow from the thorax is enhanced by rotating the
patient. In addition, kinetic rotation therapy promotes the
recruitment of previously collapsed lung areas, thus reducing the
amount of atelectasis, at identical or even lower airway pressures.
At the same time now-opened lung areas are protected from the shear
stress typically caused by the repetitive opening and closing of
collapse-prone alveoli in the dependent lung zones.
[0005] From H. C. Pape, et al.: "Is early kinetic positioning
beneficial for pulmonary function in multiple trauma patients?",
Injury, Vol. 29, No. 3, pp. 219-225, 1998 it is known to use the
kinetic rotation therapy which involves a continuous axial rotation
of the patient on a rotation bed. It has been found that the
kinetic rotation therapy improves the oxygenation in patients with
impaired pulmonary function and with post-traumatic pulmonary
insufficiency and adult respiratory distress syndrome (ARDS).
[0006] However, since the kinetic rotation therapy requires a
specially designed rotation bed it has not been found yet that the
kinetic rotation therapy justifies a broad employment. Further,
kinetic rotation therapy has been utilized with standardized
treatment parameters, typically equal rotation from greater than 45
degrees to one side to greater than 45 degrees to the other side,
and 15 minute cycle times. These rotation parameters are rarely
altered in practise due to a lack of conjoint ventilation
effectiveness and rotation activity information. Similarly, the
lack of conjoint information hampers practitioners from taking
advantage of the beneficial effects of kinetic rotation therapy by
reducing the aggressiveness of mechanical ventilation parameters
employed to treat a rotated patient.
[0007] It is an object of the invention to improve the potentials
of the kinetic rotation therapy.
[0008] This object is solved according to a first inventive
solution by a recording method for recording the status of an
artificially ventilated lung of a patient in accordance with a
plurality of lung positions, the patient lying in a nursing bed and
the position of the artificially ventilated lung is movable by a
position actuator, comprising the steps of: [0009] a) moving the
artificially ventilated lung by the position actuator to a defined
lung position, [0010] b) determining the status of the artificially
ventilated lung, and [0011] c) recording the status of the
artificially ventilated lung in accordance with the defined lung
position.
[0012] A corresponding recording apparatus according to the first
inventive solution for recording the status of an artificially
ventilated lung of a patient lying in a nursing bed in accordance
with a plurality of lung positions comprises the following
features: [0013] a) a position actuator for moving the artificially
ventilated lung to a defined lung position, [0014] b) determining
means for determining the status of the artificially ventilated
lung, and [0015] c) recording means for recording the status of the
artificially ventilated lung in accordance with the defined lung
position.
[0016] The first inventive solution is based on the cognition that
the change of the lung position of an artificially ventilated lung
also changes the status of the artificially ventilated lung.
Therefore, a reproducible recording of the status of the
artificially ventilated lung in accordance with the defined lung
position is carried out which enables a purposeful treatment of the
lung by other means.
[0017] Furthermore, the object is solved according to a second
inventive solution by a controlling method for controlling at least
one ventilation parameter of an artificial ventilator for
ventilating an artificially ventilated lung of a patient in
accordance with a plurality of lung positions, the patient lying in
a nursing bed and the position of the artificially ventilated lung
is movable by a position actuator, comprising the steps of: [0018]
a) obtaining lung status information which is based on at least two
supporting points of a first status of the artificially ventilated
lung in accordance with a first lung position and a second status
of the artificially ventilated lung in accordance with a second
lung position, [0019] b) moving the artificially ventilated lung by
the position actuator to a defined lung position, [0020] c)
controlling of at least one ventilation parameter in accordance
with the defined lung position and in accordance with the lung
status information related to said defined lung position.
[0021] A corresponding controlling apparatus according to the
second inventive solution for controlling at least one ventilation
parameter of an artificial ventilator for ventilating an
artificially ventilated lung of a patient lying in a nursing bed in
accordance with a plurality of lung positions comprises the
features of: [0022] a) means for obtaining lung status information
which is based on at least two supporting points of a first status
of the artificially ventilated lung in accordance with a first lung
position and a second status of the artificially ventilated lung in
accordance with a second lung position, [0023] b) a position
actuator for moving the artificially ventilated lung to a defined
lung position, [0024] c) means for controlling of at least one
ventilation parameter in accordance with the defined lung position
and in accordance with the lung status information related to said
defined lung position.
[0025] The second inventive solution is based on the cognition that
the change of the lung position of an artificially ventilated lung
also changes the status of the artificially ventilated lung which
can be used for an optimized ventilation. Thereby, the already
known kinetic rotation therapy can be supported. More particularly,
an optimized ventilation according to the second inventive solution
considers the fact that the top positioned lung during the rotation
therapy is relieved from superimposed pressures. For example, in
order to reach the optimum of at least one ventilation pressure
during rotation, at least a second status of the artificially
ventilated lung is determined and is compared with a previously
determined first status of the artificially ventilated lung,
wherein at least one ventilation pressure is controlled in
accordance with the difference between the first status and the
second status of the artificially ventilated lung.
[0026] Furthermore, the object is solved according to a third
inventive solution by a positioning method for controlling the
change of the position of an artificially ventilated lung of a
patient, the patient lying in a nursing bed and the position of the
artificially ventilated lung is changeable by a corresponding
position actuator, comprising the steps of: [0027] a) providing a
periodical controlling signal having a distribution of a plurality
of position periods and/or of a plurality of amplitudes, [0028] b)
controlling the position actuator by said periodical controlling
signal.
[0029] A corresponding positioning apparatus according to the third
inventive solution for controlling the change of the position of an
artificially ventilated lung of a patient lying in a nursing bed
comprises the features of: [0030] a) a position actuator for
changing the position of the artificially ventilated lung, [0031]
b) means for providing a periodical controlling signal having a
distribution of a plurality of position periods and/or of a
plurality of amplitudes, and [0032] c) means for controlling the
position actuator by said periodical controlling signal.
[0033] The third inventive solution is based on the cognition that
the parameters of the controlling signal which controls the
position actuator and thereby the lung position influences also the
success of the kinetic rotation therapy. An important parameter is
the rotation period or the movement period which is the period of
time in which the lung position returns after a movement in one
direction back to its starting position. A further cognition of the
third inventive solution is the fact that the success of the
kinetic rotation therapy can be improved if the rotation period
and/or the rotation amplitude is not fixed but varies statistically
around a predetermined mean rotation period.
[0034] The first inventive solution, the second inventive solution
and the third inventive solution can be combined with each other.
The preferred aspects described in the following can be applied to
each of the inventive solutions.
[0035] According to one aspect, the nursing bed is rotatable around
its longitudinal axis and the position actuator is a motor rotating
the nursing bed around its longitudinal axis. Alternatively, it is
also possible that the position actuator comprises air-filled or
fluid-filled cushions provided underneath the patient.
[0036] According to a further aspect, the defined lung position is
reached by a predetermined step size of the position actuator.
Alternatively, it is also possible that the defined lung position
is reached in accordance with a feed back signal of a position
sensor measuring the actual lung position.
[0037] According to a further aspect, the status of the
artificially ventilated lung is a measure of a regional or a global
information on lung morphology and/or lung function.
[0038] Regional information enables a specific treatment of a part
of the lung and can be realized by imaging methods, like the
electrical impedance tomography (EIT) or computed tomography (CT).
Global information of the lung are easier to obtain, e.g. by the
measurement of gas exchange, but measure merely the behavior of the
whole lung.
[0039] The lung morphology considers structural features of the
lung, i.e. the anatomy and its abnormalities whereas the lung
function refers to the dynamic behaviour like ventilation and blood
flow as well as to the mechanical behaviour of the lung.
[0040] According to a preferred aspect, the status of the
artificially ventilated lung is a measure of the functionality with
regard to the global gas exchange of the lung. There are multiple
methods and apparatuses for determining global gas exchange of
which some are mentioned in the following.
[0041] The status of the lung can be determined on the basis of the
CO.sub.2 concentration of the expired gas over a single breath.
Such a method and apparatus are known from the previous European
patent application "Non-Invasive Method and Apparatus for
Optimizing the Respiration for Atelectatic Lungs", filed on 26 Mar.
2004, which is herewith incorporated by reference.
[0042] Furthermore, the status of the lung can be determined on the
basis of the hemoglobin oxygen saturation (SO.sub.2). This can be
carried out by means of a saturation sensor. Advantageously, a
feedback control loop controls the inspiratory oxygen fraction
(FiO.sub.2) at the artificial ventilator such that the hemoglobin
oxygen saturation (SO.sub.2) is kept constant and a data processor
determines during a change of the airway pressure from the course
of the controlled inspiratory oxygen fraction (FiO.sub.2) an airway
pressure level which corresponds to alveolar opening or alveolar
closing of the lung. Such a method and apparatus are known from WO
00/44427 A1 which is herewith incorporated by reference.
[0043] Furthermore, the status of the lung can be determined on the
basis of the CO.sub.2 volume exhaled per unit time. Such a method
and apparatus are known from WO 00/44427 A1 which is herewith
incorporated by reference.
[0044] Furthermore, the status of the lung can be determined on the
basis of the endtidal CO.sub.2 concentration. Such a method and
apparatus are known from WO 00/44427 A1 which is herewith
incorporated by reference. Furthermore, the status of the lung can
be determined on the basis of the arterial partial pressures of
oxygen paO.sub.2. Such a method and apparatus are known from S.
Leonhardt et al.: "Optimierung der Beatmung beim akuten
Lungenversagen durch Identifikation physiologischer
Kenngro.beta.en", at 11/98, pp. 532-539, 1998 which is herewith
incorporated by reference.
[0045] According to a further aspect, the status of the lung can be
determined on the basis of the compliance of the lung, wherein the
compliance can be defined by the tidal volume divided by the
pressure difference between peak inspiratory pressure and positive
end-expiratory pressure (PIP-PEEP). Definitions of the compliance
are known e.g. from WO 00/44427 A1 which is herewith incorporated
by reference.
[0046] According to a further aspect, the status of the lung can be
determined on the basis of the inspiratory and/or expiratory
dynamic airway resistance, wherein these resistances can be defined
as the driving pressure difference divided by the flow of breathing
gases (cmH.sub.20/l/s). Definitions of the resistance are known
e.g. from WO 00/44427 A1 which is herewith incorporated by
reference.
[0047] According to a further aspect, the determined status of the
lung is sensitive to changes of alveolar dead space. The aim is to
compensate the changes of alveolar dead space by a suitable
adjustment of the positive end-expiratory pressure (PEEP) and peak
inspiratory pressure (PIP). Various methods and apparatuses are
known for determining changes of alveolar dead space of an
artificially ventilated lung which can be used separately or in
combination with each other.
[0048] According to a further aspect, the status of the lung is
determined on the basis of electrical impedance tomography data.
Such a method and apparatus are known from WO 00/33733 A1 and WO
01/93760 A1 which are herewith incorporated by reference.
[0049] Furthermore, many other known clinical methods and
apparatuses of assessment of lung function, which may combine both
gas exchange effects and hemodynamic efficiency measures, may be
employed to determine the status of the artificially ventilated
lung. Several of these include pulmonary shunt fraction, oxygen
extraction ratio, extravascular lung water, pulmonary vascular
resistance and compliance, and the like.
[0050] Furthermore, many other known clinical methods and apparati
of assessment of lung recruitment and mechanical function may be
employed to determine the status of the artificially ventilated
lung. These include upper and lower inflection points of the
expiratory and inspiratory pressure-volume curves, the point of
maximal pressure-volume compliance (Pmax), and others.
[0051] According to a further aspect, the determined status of the
artificially ventilated lung is recorded by a computer in
accordance with the corresponding defined lung position.
Preferably, the recorded data are displayed accordingly on a
screen.
[0052] The recording method and the recording apparatus according
to the first inventive solution can be used to provide a lung
status information for the controlling method and the controlling
apparatus according to the second inventive solution and for the
positioning method and the positioning apparatus according to the
third inventive solution.
[0053] According to one aspect, a predetermined differential step
size is applied repeatedly to the position actuator to obtain after
each differential step size a supporting point of the status of the
artificially ventilated lung until such supporting points of the
status of the artificially ventilated lung have been determined
over a predetermined range of lung positions.
[0054] In order to increase the resolution of the supporting
points, the lung status information can be interpolated between the
supporting points in accordance with the difference between two
neighbouring supporting points. Other interpolating methods may be
used which are based on more than two supporting points, e.g. the
least square method, by which a steady curve of the lung status
information can be obtained over the predetermined range of lung
positions.
[0055] The obtained lung status information can be used to optimize
at least one ventilation parameter of the artificially ventilated
lung over the predetermined range of lung positions according to
the second inventive solution. Preferably, at least one ventilation
parameter is controlled such that the lung status information
yields a homogeneous distribution over the predetermined range of
lung positions. Thereby, the deviations of the lung status
information over the predetermined range of lung positions can be
levelled out by applying the appropriate ventilation parameter in
accordance with the corresponding lung position. Alternatively, a
single ventilation parameter value may be determined from the
steady curve to insure maximum lung function as determined by the
lung status information over the range of lung positions.
[0056] According to a further aspect, at least one ventilation
parameter can be controlled such that the determined changes of
alveolar dead space are compensated according to the difference
between two supporting points of the lung status information of the
artificially ventilated lung. For this purpose, a characteristic
curve can be recorded for the corresponding lung showing the
relationship between alveolar dead space on the one hand and the
influence of peak inspiratory pressure (PIP) and positive
end-expiratory pressure (PEEP) thereon on the other hand. Based on
this characteristic curve the peak inspiratory pressure (PIP)
and/or positive end-expiratory pressure (PEEP) can be determined
for compensating any changes in alveolar dead space. In order to
consider additionally the rotation angle by the characteristic
curve, the status of alveolar dead space vs. PIP and/or PEEP is
determined in accordance with the plurality of lung positions.
[0057] The obtained lung status information can also be used to
optimize the controlled change of the position of an artificially
ventilated lung according to the third inventive solution.
According to the third inventive solution, a distribution of a
plurality of position periods and/or of a plurality of amplitudes
has to be provided. This can be carried out automatically on the
basis of the lung status information which is based on at least two
supporting points of a first status of the artificially ventilated
lung in accordance with a first lung position and a second status
of the artificially ventilated lung in accordance with a second
lung position. For example, a look-up table can be provided which
assigns for a specific lung status information a corresponding
control signal for the position actuator having a specific position
period and a specific position amplitude. Thereby, the controlling
signal for the position actuator is made up of a plurality of curve
pieces over the predetermined range of lung positions which yields
over time a distribution of position periods and/or amplitudes.
[0058] Alternatively, the distribution can be compiled via a user's
interface on the basis of a given set of periodical controlling
signals for providing a predetermined distribution.
[0059] Alternatively, the distribution can be compiled
automatically in advance or online and can follow a known
probability distribution or can follow a biologic variability. For
example, the human's heartbeat follows a characteristic biologic
variability which can be scaled and adapted to provide for the
described purpose.
[0060] Other objects and features of the invention will become
apparent by reference to the following specifications, in which
[0061] FIG. 1 shows an example of a nursing bed according to the
invention,
[0062] FIG. 2 shows a first example of a position actuator in a
horizontal position,
[0063] FIG. 3 shows the first example of a position actuator in an
angulated position,
[0064] FIG. 4 shows a second example of a position actuator in a
horizontal position,
[0065] FIG. 5 shows the second example of a position actuator in an
angulated position,
[0066] FIG. 6 shows a schematic monitoring screen for the method
for controlling at least one ventilation pressure,
[0067] FIG. 7 shows an alveolar recruitment maneuver during kinetic
rotation therapy,
[0068] FIG. 8 shows the titration process after a successful lung
recruitment maneuver has been performed during kinetic rotation
therapy,
[0069] FIG. 9 shows an artificial ventilation of a lung by
controlling the PIP and the PEEP in accordance with the rotation
angle,
[0070] FIG. 10 shows a schematic monitoring screen when controlling
the PIP and PEEP during the rotation cycle according to FIG. 9,
[0071] FIG. 11 shows the measurements of paO.sub.2, paCO.sub.2, and
pHa during the kinetic rotation therapy, and
[0072] FIG. 12 shows the measurement of compliance during kinetic
rotation therapy.
[0073] FIG. 1 shows an example of a nursing bed according to the
invention. The nursing bed 101 is mounted such that it can be
rotated around its longitudinal axis, as indicated by the arrow
102. The rotation angle is changeable by a position actuator 103,
which is controlled by a control unit 104.
[0074] The patient 105 is fixed on the nursing bed 101 and is
artificially ventilated by the ventilator 106. The position
actuator 103 can be controlled by the control unit 104 such that
the patient is turned resulting in a defined lung position of the
artificially ventilated lung. The lung position refers to the
rotation angle of the lung being 0.degree. if the patient is lying
horizontally on the bed, which itself is positioned horizontally.
Measurements of the lung position can be performed by employing a
portable position sensor attached to the patient's thorax and
connected to the control unit 104. The nursing bed 101 shown in
FIG. 1 allows also to determine the rotation angle of the patient's
lung through a measurement of the rotation angle of the nursing bed
101.
[0075] The status of the artificially ventilated lung can be
determined by a variety of methods using a suitable measurement
device 107. The measurement device 107 can for example use data
such as airway pressures, constitution of the expired gas, and the
volume of the inspired and expired gas obtained from the artificial
ventilator to determine the status of the lung. The measurements to
determine the status of the lung can either be performed
continuously or sporadically at defined lung positions. Examples of
methods to determine the status of the lung are given below: [0076]
The status of the lung is determined on the basis of the CO.sub.2
concentration of the expired gas over a single breath. Such a
method and apparatus are known from the European patent application
"Non-Invasive Method and Apparatus for Optimizing the Respiration
for Atelectatic Lungs", filed on 26 Mar. 2004, which is herewith
incorporated by reference. [0077] The status of the lung is
determined on the basis of the hemoglobin oxygen saturation
(SO.sub.2). This can be carried out by means of a saturation
sensor. Advantageously, a feedback control loop controls the
inspiratory oxygen fraction (FiO.sub.2) at the artificial
ventilator such that the hemoglobin oxygen saturation (SO.sub.2) is
kept constant and a data processor determines during a change of
the airway pressure from the course of the controlled inspiratory
oxygen fraction (FiO.sub.2) an airway pressure level which
corresponds to alveolar opening or alveolar closing of the lung.
Such a method and apparatus are known from WO 00/44427 A1 which is
herewith incorporated by reference. [0078] The status of the lung
is determined on the basis of the CO.sub.2 volume exhaled per unit
time. Such a method and apparatus are known from WO 00/44427 A1
which is herewith incorporated by reference. [0079] The status of
the lung is determined on the basis of the endtidal CO.sub.2
concentration. Such a method and apparatus are known from WO
00/44427 A1 which is herewith incorporated by reference. [0080] The
status of the lung is determined on the basis of the arterial
partial pressures of oxygen paO.sub.2. Such a method and apparatus
are known from S. Leonhardt et al.: "Optimierung der Beatmung beim
akuten Lungenversagen durch Identifikation physiologischer
Kenngro.beta.en", at 11/98, pp. 532-539, 1998 which is herewith
incorporated by reference. [0081] The status of the lung is
determined on the basis of the compliance of the lung, wherein the
compliance can be defined by the tidal volume divided by the
pressure difference between peak inspiratory pressure and positive
end-expiratory pressure (PIP-PEEP). Definitions of the compliance
are known e.g. from WO 00/44427 A1 which is herewith incorporated
by reference. [0082] The status of the lung is determined on the
basis of the inspiratory and/or expiratory dynamic airway
resistance, wherein these resistances can be defined as the driving
pressure difference divided by the flow of breathing gases
(cmH.sub.20/l/s). Definitions of the resistance are known e.g. from
WO 00/44427 A1 which is herewith incorporated by reference. [0083]
The status of the lung is determined on the basis of electrical
impedance tomography data. Such a method and apparatus are known
from WO 00/33733 A1 and WO 01/93760 A1 which are herewith
incorporated by reference.
[0084] In the following, an example of a treatment of the patient
will be described which will be explained thereafter in more detail
by means of the FIGS. 2-12.
Recruitment Maneuver
[0085] At 0.degree. rotation angle PEEP is adjusted above the
expected alveolar closing pressure (depending on the lung disease
between 15 and 25 cmH.sub.2O). PIP is set sufficiently high above
PEEP to ensure adequate ventilation.
[0086] Then rotation is started. Each lung is opened separately
while it is moved into the upward position.
[0087] With increasing rotation angle, a stepwise increase of the
PIP starts 5-20 breaths prior to reaching the maximum rotation
angle, PIP reaches its maximum value (depending on the lung disease
between 45 and 65 cmH.sub.2O) at the maximum rotation angle.
[0088] Having crossed the maximum rotation angle PIP is decreased
within 5-20 breaths.
[0089] After each lung has been recruited separately (by rotating
the patient to both sides) in the above manner, PIP is adjusted for
each lung separately to maintain adequate ventilation.
PEEP Titration for Finding the Closing PEEP
[0090] After a recruitment maneuver, PEEP is decreased continuously
with increasing rotation angles. The status of the artificially
ventilated lung is recorded continuously. Starting at a given PEEP
at a rotation angle of 0.degree., PEEP will be lowered such that at
maximum rotation angle PEEP will be reduced by 1-2 cmH.sub.2O
(procedure 1). If no signs for alveolar collapse occur in any of
the above signals the level of PEEP is recorded and will be
increased continuously to the previous setting when at 0.degree..
While turning the patient to the other side PEEP is reduced in the
same way (procedure 2). If no signs for alveolar collapse occur in
any of the above signals, the level of PEEP is then kept at this
value and the patient is turned back to 0.degree..
[0091] If no collapse is present at a rotation angle of 0.degree.
the procedures 1 and 2 are carried out at reduced PEEP levels until
signs of alveolar collapse occur. The level of PEEP at which this
collapse occurs is then recorded for the respective side. The PEEP
will be increased continuously to the previous setting when at
0.degree. while turning the patient back to 0.degree.. If due to a
hysteresis behaviour of the lung signs of a lung collapse are still
present, a recruitment maneuver will be performed at this stage to
re-open the lung as described above.
[0092] Continuing with an open lung condition, the PEEP is set 2
cmH.sub.2O above the known closing pressure for the side for which
the lung collapse occurred.
[0093] Thereafter, PEEP is reduced in the way described above while
turning the patient to the opposite side for which the closing
pressure is not yet known. Once collapse occurs also for this side,
PEEP is recorded and the lung is reopened again.
Controlling the Ventilation Parameters During Rotation
[0094] After having determined the PEEP collapse pressure of each
side, PEEP will be adjusted continuously with the ongoing rotation
while making sure that PEEP never falls below the levels needed for
each one of the sides.
[0095] Since PEEP and compliance may vary with the rotation angle
adjustments are needed. Therefore, during rotation therapy PIP
levels are adjusted continuously from breath to breath in
accordance with the difference between a first status and a second
status of the artificially ventilated lung in order to ventilate
the patient sufficiently while keeping tidal volumes within a
desired range of 6-10 ml/kg body weight.
[0096] Furthermore, if PIP pressures are at very low values
already, it might be advisable to leave PIP constant but adjust for
changes in compliance by adjusting the respiratory rate (RR). Then,
RR is adjusted continuously from breath to breath in order to
ventilate the patient sufficiently while keeping PIP constant.
[0097] It has been shown that the variation of the rotation period
improves the effect of the kinetic rotation therapy even further.
For example, the following modes of variation can be applied:
[0098] Sinusoidal variation with wave length between several
minutes to several hours with set minimum and maximum values for
ration angles, speeds and resting periods. [0099] Ramp like
variation within certain boundaries with ramp periods between
several minutes to several hours and set minimum and maximum values
for rotation angles, speeds and resting periods. [0100] Random
variation about a given mean value at a single level of variability
(i.e. biologic variability) with amplitudes between 50% to 200% of
mean sequence of magnitude of this parameter from a uniform
probability distribution between e.g. 0% to 100% of its chosen mean
value. [0101] Variability can be determined according to technical
approaches covering the whole range from allowed minimum to
maximum. [0102] Distribution of rotation parameters can be Gaussian
or biological.
[0103] In addition to the rotation period the rotation angle, the
rotation speed and the resting periods can be varied. In order to
adjust for variable rotation angles, speed and resting times, a
mean product of angle and resting period etc can be defined, that
needs to be kept constant. For example: [0104] While rotation angle
randomly varies about a given rotation angle, resting periods are
adjusted to keep the product of angle and time approximately
constant at a given rotation speed. [0105] While rotation angle
randomly varies about a given rotation angle, rotation speed is
adjusted to keep the product of angle and speed approximately
constant while no resting period is applied.
[0106] FIG. 2 shows a first example of a position actuator in a
horizontal position representing the initial position. The
schematic drawing depicts the patient 201 lying in the supine
position. As defined in medical imaging, the patient is looked at
from the feet, thus the right lung (R) is on the left hand side of
FIG. 2, and the left lung (L) is on the right hand side of FIG. 2,
while the heart (H) is located centrally and towards the front.
[0107] It should be noted in this connection that the methods
according to the invention can be equally well applied to patients
lying in the prone position.
[0108] The patient is lying on a supporting surface 202, which
covers three air-cushions 203, 204 and 205. These air-cushions,
being mounted to the fixed frame 206 of the nursing bed, are
inflated in this horizontal position of the nursing bed with a
medium air pressure. The air pressure of the air-cushions 203, 204
and 205 can be adjusted by a control unit either by pumping air
into an air-cushion or by deflating an air-cushion. Obviously,
other fluids than air could be used as well.
[0109] Changing the air pressure in the air-cushions 203, 204 and
205 in a particular fashion leads to a rotation of the supporting
surface 202 and hence to a rotation of the artificially ventilated
lung. By simultaneous measurements of the rotation angle of the
artificially ventilated lung, i.e. through an attached position
sensor at the patient's thorax, the rotation angle of the
artificially ventilated lung can be adjusted to defined positions.
Alternatively, a defined lung position can be reached by a
predetermined step size of the position actuator, i.e. a
predetermined air pressure within each air-cushion.
[0110] FIG. 3 shows the first example of the position actuator in
an angulated position resulting from a specific setting of the air
pressures in the air-cushions. Compared to FIG. 2, in this
particular example the air pressure of the air-cushion 303 has been
lowered, the air pressure of the air-cushion 304 has not been
changed, and the air pressure of the air-cushion 305 has been
raised.
[0111] This results in a rotation of the supporting surface 302 and
thus in a rotation of the artificially ventilated lung. Noticeably,
the frame 306 of the nursing bed remains in its horizontal
position.
[0112] FIG. 4 shows a second example of a position actuator in a
horizontal position representing the initial position. The
schematic drawing depicts the patient 401 lying in the supine
position as defined in the description of FIG. 2.
[0113] The patient is lying on a supporting surface 402, which is
attached to the frame 403 of the nursing bed. The frame 403 can be
rotated by a motor which represents the position actuator according
to signals received from a control unit. A rotation of the frame
403 results directly in a rotation of the patient and hence the
artificially ventilated lung. By simultaneous measurements of the
rotation angle of the artificially ventilated lung, i.e. through
measurements of the rotation angle of the frame 403, the rotation
angle of the artificially ventilated lung can be adjusted to
defined positions. Alternatively, a defined lung position can be
reached by a predetermined step size of the position actuator, i.e.
performing a predetermined number of steps using a step motor.
[0114] FIG. 5 shows the second example of a position actuator in an
angulated position, resulting from a specific setting of the
position actuator. In this particular setting of the position
actuator the left lung of the patient is elevated. The supporting
surface 502 and the frame 503 of the nursing bed are both
rotated.
[0115] FIG. 6 shows a schematic monitoring screen for the method
for controlling at least one ventilation pressure. Displayed are
both the input of the artificial ventilation system in form of the
PIP and the PEEP as well as an example of a physiological output
information of the patient in form of the on-line SpO.sub.2 signal.
The SpO.sub.2 signal represents the oxygen saturation level. The
values of the PIP, the PEEP, and SpO.sub.2 are plotted in a
circular coordinate system over the rotation angle of the
artificially ventilated lung. The rotation angle is depicted in
FIG. 6 through the dashed lines for values of -45.degree.,
0.degree., and 45.degree.. The values for the PIP, the PEEP, and
SpO.sub.2 can be obtained from the graph using an axis
perpendicular to the axis of the particular rotation angle.
[0116] As can be seen from FIG. 6, when the nursing bed turns the
patient towards a negative rotation angle, the value of the
SpO.sub.2 signal increases substantially, whereas the value of the
SpO.sub.2 signal decreases, when the patient is turned towards a
positive rotation angle.
[0117] This variation of the SpO.sub.2 signal relates to constant
values of the PIP and the PEEP. Without changing at least one of
the airway pressures the evaluation of the SpO.sub.2 signal of the
patient during a rotation would only represent a diagnostic goal.
Therefore, FIGS. 7-10 represent the effects of controlling at least
one ventilation pressure on a physiological output information.
[0118] FIG. 7 shows an alveolar recruitment maneuver during kinetic
rotation therapy Before the recruitment maneuver starts at
0.degree. rotation angle, the PEEP is adjusted above the expected
alveolar closing pressure (depending on the lung disease between 15
and 25 cmH.sub.2O). The PIP is set sufficiently high above the PEEP
to ensure adequate ventilation.
[0119] During the recruitment maneuver the PIP is stepwise
increased such that as many lung units as possible are re-opened,
while at the same time the PEEP is maintained at a level to keep
the newly recruited lung units open. The recruitment is applied
towards the maxima of the positive and the negative rotation
amplitudes where the respective upper lung is relieved from almost
all superimposed pressures. Therefore, each lung is opened
separately while it is moved into the upward position.
[0120] For example the stepwise increase of the PIP can start 5-20
breaths prior to reaching the maximum rotation angle and the PIP
reaches its maximum value (depending on the lung disease between 45
and 65 cmH.sub.2O) at the maximum rotation angle. Having crossed
the maximum rotation angle the PIP is decreased within 5-20 breaths
to its initial value.
[0121] After each lung has been recruited separately (by rotating
the patient to both sides) in the above manner, PIP can be adjusted
for each lung separately to maintain adequate ventilation.
[0122] FIG. 8 shows the titration process after a successful
alveolar recruitment maneuver has been performed during kinetic
rotation therapy.
[0123] Due to the hysteresis behaviour of the lung, the values
obtained for the PIP and for the PEEP during the alveolar
recruitment maneuver are too high to further ventilate the lung
with these airway pressures once the lung units have been
recruited. Thus they need to be reduced systematically during the
titration process. The goal is to obtain the minimum values for the
PEEP for specific rotation angles that would just keep all lung
alveoli open. For further ventilation the PEEP can be set slightly
above these values and the PIP can be adjusted according to the
desired tidal volume.
[0124] As shown in FIG. 8A the PIP and the PEEP are reduced,
typically in periods of one step-wise reduction per minute, towards
both maxima of the rotation amplitude. The titration process begins
with decreasing the PIP and/or the PEEP when rotating the
artificially ventilated lung towards positive rotation angles
(procedure 1). When the artificially ventilated lung is returned to
the initial position, i.e. 0.degree. rotation angle, the PIP and
the PEEP are set to their initial values. The PIP and/or the PEEP
are reduced again once the artificially ventilated lung is rotated
towards negative rotation angles (procedure 2). As an example of a
physiological feedback parameter the oxygen saturation signal
SpO.sub.2 is shown in FIG. 8A as a dashed line. The oxygen
saturation remains constant during the entire rotation cycle
(procedure 1+procedure 2), indicating that no significant collapse
occurred. Thus the titration process has to continue.
[0125] In order to increase the likelihood of a collapse of lung
units, each subsequent rotation cycle starts with lower values for
the PIP and for the PEEP. FIG. 8B represents a further rotation
cycle of the titration process. The oxygen saturation signal
SpO.sub.2 remains again constant during the rotation cycle shown in
FIG. 8B, indicating that the lowest values of the PEEP reached at
the maximum rotation angles are still too high to result in a
significant collapse of lung units.
[0126] A further reduction of the PIP and the PEEP has been
performed before commencing the next rotation cycle as shown in
FIG. 8C. When turning the patient to positive rotation angles and
reducing the PEEP (procedure 1), the oxygen saturation signal
SpO.sub.2 shows a variation in form of a reduction. Once this
variation has been identified, no further reductions of the airway
pressures are performed. The PEEP corresponding to the point when
the variation of the oxygen saturation signal SpO.sub.2 has been
identified represents the collapse pressure for the particular
rotation angle. The titration process for positive rotation angles
is finished.
[0127] When turning the patient back towards the initial position,
i.e. 0.degree. rotation angle, the PIP and the PEEP are set to
their original values. The oxygen saturation signal SpO.sub.2
recovers to its initial value. As indicated in FIG. 8C a hysteresis
effect is usually present.
[0128] When turning the patient to negative rotation angles the PIP
and/or the PEEP are reduced in order to identify the collapse
pressure for negative rotation angles (). The oxygen saturation
signal SpO.sub.2 remains constant, indicating that the value of the
PEEP reached at the maximum negative rotation angle is still too
high to result in a significant collapse of lung units.
Consequently, the titration process at negative rotation angles has
to continue.
[0129] A further rotation cycle starting once more with lower
values for the PIP and for the PEEP is shown in FIG. 8D. As
indicated, collapse pressures for positive and for negative
rotation angles can be identified according to the procedure of
FIG. 8C. The collapse pressure for the positive rotation angle,
corresponding to the value already obtained in FIG. 8C, is lower
than the collapse pressure for the negative rotation angle.
[0130] After having identified the collapse pressures for positive
and negative rotation angles a recruitment maneuver according to
FIG. 7 needs to be carried out in order to re-open lung units which
collapsed during the titration process. As mentioned before, such a
re-opening procedure can become necessary already during the
titration process once the collapse pressure for one side has been
identified. This is the case, if, due to a hysteresis behaviour of
the lung, signs of lung collapse continue to be present when the
patient is turned back to 0.degree. and the PEEP is raised to its
previous setting when at 0.degree..
[0131] Once the lung is fully recruited again, the PEEP levels are
set for the positive and negative rotation angles separately
according to the collapse pressures as identified before. A safety
margin of i.e. 2 cmH.sub.2O is added to each collapse pressure.
Eventually, the PIP can be adjusted according to the desired tidal
volume.
[0132] FIG. 9 shows an artificial ventilation of a lung by
controlling the PIP and the PEEP in accordance with the rotation
angle. Based on the collapse pressures for positive and for
negative rotation angles, as identified according to FIG. 8, a
curve for the PEEP as a function of the rotation angle can be
established. The shape of the curve, having in this particular
example a smooth curvature, can be chosen freely, provided a safety
margin is realized in order to keep the PEEP above the
corresponding collapse pressure. The curve of the PIP as a function
of the rotation angle follows directly from the corresponding PEEP
value and the desired tidal volume.
[0133] Controlling the PIP and the PEEP as a function of the
rotation angle in this way leads to an optimal ventilation of the
lung. The oxygen saturation signal SpO.sub.2 remains constant
during the rotation cycle while at the same time, due to the lowest
possible values for the PIP and the PEEP, no lung over-distension
is present and the desired tidal volume is achieved.
[0134] FIG. 10 shows a schematic monitoring screen when controlling
the PIP and the PEEP during the rotation cycle according to FIG. 9.
The presentation of the PIP, the PEEP, and the SpO.sub.2 with
respect to the rotation angle is identical to that of FIG. 6.
[0135] By controlling the PIP and the PEEP according to the
rotation angle it is possible to keep the oxygen saturation signal
SpO.sub.2 constant during a rotation cycle. This is in contrast to
FIG. 6 where the oxygen saturation signal SpO.sub.2 decreased with
increasing rotation angles, i.e. due to the collapse of lung units.
This collapse is prevented within the artificial ventilation shown
in FIG. 10 by controlling the PIP and the PEEP accordingly.
[0136] FIG. 11 shows the measurements of paO.sub.2, paCO.sub.2, and
pHa during the kinetic rotation therapy. As it can be seen,
paO.sub.2 improves continuously during the kinetic rotation
therapy. The rotation period was switched during kinetic rotation
therapy from 8 to 16 rotation periods per hour. Having a mean
ventilation frequency of 10 to 40 breaths per minute this results
in 50 to 250 breaths per rotation period.
[0137] The schematic drawing of FIG. 11 is derived from an original
on-line blood gas registration by the blood gas analyzer Paratrend
(Diametrics, High Newcombe, UK) of a patient suffering from adult
respiratory distress syndrome (ARDS) who is treated in a nursing
bed employing a Servo 300 ventilator (Siemens Elema, Solna,
Sweden). Rotation angles ranged from -62.degree. to +62.degree.0.
While the mean paO.sub.2 improves continuously during the kinetic
rotation therapy, paO.sub.2 also oscillates around a mean value
resulting from turning the patient from one side to the other. The
oscillation reflects the fact that artificially ventilating the
patient at one side seems to be more effective for improving
paO.sub.2 than artificially ventilating the patient at the other
side.
[0138] Without additional data the blood gas analysis does not give
any information about the relationship between the rotation angle,
the ventilator settings and their final effect on gas exchange. The
registration shows, however, the influence of the rotation period
on the mean paO.sub.2 and its oscillations. As stated above, in
this particular example the rotation period was switched from 8 to
16 rotation periods per hour. While paO.sub.2 increased, the
amplitude of the oscillations was considerably reduced, indicating
that the individual and time dependent influences of the sick lung
and the normal lung are minimized.
[0139] It becomes obvious that a link between at least two of the
factors rotation angle, ventilator settings, and physiological
output variable is needed.
[0140] FIG. 12 shows a measurement of the compliance during the
kinetic rotation therapy. As expected, the compliance improves
during the kinetic rotation therapy. As explained above, the
ventilation parameters are adapted accordingly. It should be noted,
that the range of the rotation angle shown in FIG. 12 represents
only one example. Higher values for the rotation angle, i.e.
.+-.90.degree. or even more, can be chosen if required.
[0141] The compliance is displayed as a function of the rotation
angle. When the patient is turned towards +62.degree. rotation
angle (following the bold line from its beginning at 0.degree.
rotation angle) the compliance decreases to almost half of its
initial value at 0.degree. rotation angle. As the patient is turned
back to the initial position at 0.degree. rotation angle, the
compliance increases even beyond the initial value and continues to
improve as the patient is turned towards negative rotation angles.
The compliance reaches its temporary maximum at -62.degree.
rotation angle. As the patient is turned back to the initial
position at 0.degree. rotation angle, the compliance decreases
continuously but remains significantly above the value at the
previous zero-degree-transition. As kinetic rotation therapy
continues, the compliance values follow a similar pattern as
described, however, the incremental improvements per rotation cycle
become smaller and it is apparent that a certain saturation of the
therapeutic effect has been reached. For the sake of an even
further improvement of the lung function, a superimposed active
therapeutic intervention like an alveolar recruitment maneuver by
means of a ventilator should be applied.
* * * * *